Wireless network devices typically need to be synchronized with each other in order to avoid a large timing offset which can impact the correct reception of wireless data. Accordingly, it is known to derive the timing for the network communication protocol from a local master clock.
In a wireless network device, e.g. magnetic induction (MI)-based, the local master clock can be the RC oscillator of the (MI) physical layer, the master clock of an audio interface or an external crystal oscillator. An on-chip local oscillator of the device's protocol processor is then locked to this master clock, and used to determine the timing network communication. Typically, the RC oscillator of the MI physical layer is used as the device local master clock in order to limit power consumption and to spare the required physical space (in other words, no external crystal oscillator is required).
The RC oscillator of an MI physical layer (used as device local master clock) can deviate up to 1% from its nominal value due to factors such as power supply voltage variations and local on-chip temperature changes. Hence, the oscillator frequency of the different network devices typically needs to be synchronized in order to avoid large timing offset which impact the correct reception of wireless frames.
Wireless frames are typically divided into specific and standardized sections. By way of example, a wireless frame typically has a MAC header, payload and Frame Check Sequence (FCS). Wireless frames may be organized in a larger structure, which can be identified as a superframe. A superframe may be divided in a number of timeslots and a wireless frame may occupy one or more timeslots in such a superframe. A superframe may also contain a beacon frame to indicate the start of the superframe.
The conventional method used to keep network devices in sync is to frequently send beacon frames. However, frequent beacon frame transmission consumes bandwidth which reduces the protocol streaming efficiency. Furthermore, if only the beacon frame is used for time synchronization, a frequency deviation of e.g. 0.5% will cause a full timeslot miss-alignment at the end of a typical superframe having 256 timeslots.